#U3 Pro spot welder

A monster fan hand-built on 6 × 32140 cells. The 3D-printed model is his own design, prints well, and the whole structure is joined with heat-set inserts. The motor is a 3660KV brushless paired with aluminium blades; the small motor can burst to 1200W. Insulating rings go on the cells, then spot welding with the AWithZ U3 welder set to manual; the motor is rated 1200W, which by Ohm’s law is about 100A, and this nickel strip passes at most 33A, so three layers of nickel are stacked one after another to make sure the cells can deliver their full discharge rate; the welds come out perfectly smooth. Cells in, fan housing and grip screwed together, done; thrust tested at over 1000 grams. Comments: asking for the files (×2), no mould needed?, how much did it cost, ‘1200W? my e-bike is only 1200W’.

Opens with ‘I’m hooked, taking my ex’s cleaver to unwind, weld weld weld’, then ‘real work comes first’. Process (no narration, watching the footage): CNC-mill small copper tabs (comment: 1mm copper plate is a bit thick and won’t take a weld, hence small tabs); 3D-print a four-hole cell holder; caliper measurement; laser engraving; four cells (14500/16340-class small cells) go into the holder, the U3 Pro spot-welds nickel strip into 2S2P; multimeter reads about 7V (2S); green heat-shrink seals it into a flashlight pack that goes into a Wurkkos SP10-class 8.4V light; ‘open for business +1’. 73 comments: how much sponsorship did you take, even 1.5 nickel-plated is a struggle, badly over-rated, just returned mine (no sponsorship money exists); not even a BMS? (no suitable board, the stock battery has no balance board either, a generic board won’t fit in a flashlight, a small board trips output protection the moment the light turns on); thought you’d weld the copper on directly (1mm copper plate is a bit thick, won’t take a weld); CNC and Fluke too, the weak student has the most tools; will careless welding hurt the discharge cap’s life (liked by the creator).

A friend brought over a faulty pesticide sprayer; a check showed the battery had been drained dead, so a new Li-ion pack is made. Parts: battery box, connecting nickel strip, BMS, 18650 cells — HIGHSTAR ISR18650-2500 cells, 2500mAh; measured 4.2V, internal resistance 15.7/16, consistency is decent. The welder is an AWithZ U3 (nameplate: spot-weld output voltage 4.2V MAX, output current 650A MAX, Type-C input 5V/2.1A, USB output 5V/2.4A, battery 11000mAh 3.7V 40.7Wh, manufacturer Shenzhen Juequi Technology), only palm-sized, 11000mAh battery, 2-inch HD screen, 80 adjustable gears, manual trigger button; not just a spot welder but also a power bank. Weld strength test: the nickel strip tore and the weld still didn’t let go. The pack is 12V, three in series, three in parallel; the BMS is soldered to the cells in order; 4.2V, 8.4V and 12.6V all check out, so the welds are fine; the pack’s positive and negative leads are soldered to the terminals on the housing; the housing is sealed with glue; fitted, switch on, water comes out — perfect repair. Comments: it’s a sprayer, not a spray (liked by the creator); a 3S2P with a BMS gave no output even after swapping several boards; 9 cells isn’t enough; swap the original lead-acid for Li-ion and one charge on the lead-acid charger and “uh-oh”.